Pyrolytic decomposition of silicon-bearing gas in fluidized beds is an attractive process for producing polysilicon for the photovoltaic and semiconductor industries due to excellent mass and heat transfer, increased surface for deposition, and continuous production. Granular silicon prepared by pyrolytic decomposition of a silicon-bearing gas, particularly monosilane, typically comprises a small amount of hydrogen, such as 10-20 ppmw hydrogen. However, electronic-grade granular silicon desirably includes 5 ppmw hydrogen or less. The hydrogen content can be reduced by heat treatments, such as by annealing, whereby hydrogen diffuses out of the silicon. A need exists for a device and method suitable for continuous annealing of granular silicon.